Laser systems may be useful for many different applications. More particularly, tunable laser systems capable of emitting one or more optical beams over a range of wavelengths are presently used in applications including, without limitation, seed for optical amplifiers, multi-photon microscopy, optical coherence tomography, and harmonic generation. For some such applications, lasers having ultra-short pulse widths which are tunable over a range of lasing wavelengths may be desirable. While such attributes may be desirable, the modalities utilized within a laser system to generate these features may create practical difficulties. For example, a tunable laser that is configured to operate over a range of lasing wavelengths may be difficult to stabilize over the full tuning range because the interaction of the laser light with the optics of the system may be wavelength dependent. This phenomenon may be exacerbated in a laser system that produces ultra-short pulses that are sensitive to the dispersive properties of the optical system.
Solid state ultra-short pulse oscillators are well known and Ti:Sapphire is a commonly used gain medium to achieve pulse widths in the femto second range with these lasers. Typical pulse widths of commercial fs-oscillators may range from less than about 10 fs to about 1 picosecond. Oscillators with a tunable center wavelength or fixed center wavelength, but in any case no independent bandwidth control, have been offered commercially since the early 1990s. Lasers of this kind may be optimized to provide a predetermined bandwidth, which may result in a fixed pulse width for the laser output.
Due to the complexity of physical interactions between light and the optical elements of such systems, control or adjustability of a center wavelength and bandwidth may involve a number of difficulties. Maintaining optimal parameters in a multi-dimensional parameter space includes substantial challenges when trying to keep such a laser operational throughout a tuning process. The complexity of the task has not allowed for a commercial offering of a laser system in which the oscillator bandwidth can be tuned under hands-off conditions while simultaneously controlling the center wavelength of the emitted radiation.
While development efforts have been previously undertaken, the lacking market need and the state-of-the-art of the technology weren't sufficient for commercialization of such laser system. However, emerging applications in bio-science and chemistry as well as life and health science over recent years have increased the need to have hands-off, wavelength and bandwidth tunable seed sources as flexible tools for scientific applications.
What have been needed are stable and reliable tunable laser systems that operate with an ultra-short pulse width and which are automatically tunable and stable over a broad range of operating wavelengths and bandwidths. What has also been needed are such tunable laser systems with output beams which are stable over the entire operating range of wavelengths and bandwidths without the need for external adjustment and which are capable of maintaining stable pulses over the entire tunable range.